1) Field
The general inventive concept relates to a method of preparing a field electron emitter and, more particularly, to a method of preparing a carbon nanotube field electron emitter and a field electron emission device including a carbon nanotube field electron emitter prepared by the method.
2) Description of the Related Art
In general, in electron emission devices, electrons are emitted from a field electron emitter in a cathode electrode by an electric field generated when a voltage is applied between the cathode electrode and an anode electrode. The electrons collide with a phosphor material on the anode electrode, and light is thereby emitted.
Since carbon nanotubes (“CNTs”) exhibit excellent conductivity, excellent field concentration and emission properties and a low work function, as compared to other nanotubes, CNTs are more easily driven at a low voltage and are more easily manufactured to have a large area. Thus, CNTs are being increasingly utilized as field electron emitters.
CNTs generally include materials having cylindrical carbon molecules in which three carbon atoms are bonded to a fourth carbon atom in a hexagonal honeycomb shape. A typical carbon nanotube may have a diameter of several nanometers and a length of up to several millimeters. CNTs include a chemical bond having sp2 bonds, similar to those of graphite, and a hexagonal lattice of carbon atoms, e.g., a graphite layer. CNTs are categorized as either single walled carbon nanotubes (“SWCNTs”) or multi-walled carbon nanotubes (“MWCNTs”), based on whether a number of graphite layers of the particular CNTs is singular or plural, respectively. When SWCNTs are formed in a shape such as that of a bundle, SWCNTs are further referred to as bundle-type SWCNTs. Furthermore, CNTs, whether SWCNTs or MWCNTs, may have properties of electrical conductors and/or semiconductors, based on a structure of the graphite layers.
In addition, CNTs have large specific surface area, high conductivity, uniform distribution of pores, high mechanical strength and stable chemical properties, as compared to other types of field electron emitters.
Methods of preparing field electron emitters for emitters in field effect electron emission devices and, more specifically, methods of preparing field electron emitters containing CNTs include a carbon nanotube growing method using a chemical vapor deposition (“CVD”) method, a paste method using a composition for forming field electron emitters that contain CNTs and an electrophoretic deposition method, for example. When CNTs are deposited on a substrate in the electrophoretic deposition method, the CNTs are electrophoretic-deposited on the substrate while being dispersed in an organic solvent such as acetone, ethanol, dimethylformamide (“DMF”) or benzene, for example. When the organic solvent is used in the electrophoretic-deposition method, a material not dissolved in the organic solvent, such as an inorganic material for example, forms a device structure on the substrate. In addition, a high voltage is applied in the electrophoretic deposition method, and it is therefore difficult to form a uniform field electron emitter.